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[PATCH] adapt page_lock_anon_vma() to PREEMPT_RCU

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page_lock_anon_vma() uses spin_lock() to block RCU.  This doesn't work with
PREEMPT_RCU, we have to do rcu_read_lock() explicitely.  Otherwise, it is
theoretically possible that slab returns anon_vma's memory to the system
before we do spin_unlock(&anon_vma->lock).

[ Hugh points out that this only matters for PREEMPT_RCU, which isn't merged
  yet, and may never be.  Regardless, this patch is conceptually the
  right thing to do, even if it doesn't matter at this point.  - Linus ]

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Acked-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2007-02-28 20:13:49 -08:00 committed by Linus Torvalds
parent 48dba8ab9b
commit 34bbd70405
1 changed files with 13 additions and 4 deletions
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17
mm/rmap.c
View file

@ -183,7 +183,7 @@ void __init anon_vma_init(void)
*/
static struct anon_vma *page_lock_anon_vma(struct page *page)
{
struct anon_vma *anon_vma = NULL;
struct anon_vma *anon_vma;
unsigned long anon_mapping;
rcu_read_lock();
@ -195,9 +195,16 @@ static struct anon_vma *page_lock_anon_vma(struct page *page)
anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
spin_lock(&anon_vma->lock);
return anon_vma;
out:
rcu_read_unlock();
return anon_vma;
return NULL;
}
static void page_unlock_anon_vma(struct anon_vma *anon_vma)
{
spin_unlock(&anon_vma->lock);
rcu_read_unlock();
}
/*
@ -333,7 +340,8 @@ static int page_referenced_anon(struct page *page)
if (!mapcount)
break;
}
spin_unlock(&anon_vma->lock);
page_unlock_anon_vma(anon_vma);
return referenced;
}
@ -802,7 +810,8 @@ static int try_to_unmap_anon(struct page *page, int migration)
if (ret == SWAP_FAIL || !page_mapped(page))
break;
}
spin_unlock(&anon_vma->lock);
page_unlock_anon_vma(anon_vma);
return ret;
}